Due in large part to environmental concerns, the management of trash and refuse disposal has become very important. As a given population increases, the amount of trash generated also increases. This situation is complicated by the fact that the public demand for disposable goods is seemingly insatiable. More and more products ranging from food items to industrial machinery are provided in containers made of "disposable" polystyrenes and like compounds. Even if a given population were to remain constant in number, the amount of trash generated by that population continues to increase. Thus, it has become necessary to develop techniques and equipment that can process and dispose of greater and greater amounts of trash.
A primary stage in trash management is collection. It is well known to use a large or industrial receptacle such as a dumpster at places of high population density such as apartments, condominiums, office buildings, malls, etc. Individuals typically place trash into the receptacle (often referred to as a dumpster or container), where it is picked up by a truck or some other vehicle that hauls the trash to a recycling center, landfill or to an incinerator. The receptacle is of a fixed volume and limited in the amount of trash it can hold. Similarly, the truck is of a fixed volume and its capacity limited accordingly. To expand this capacity, it has become commonplace to equip the truck, the receptacle or both, with a compactor that reduces the volume of trash. The compactor crushes the trash into a smaller volume by increasing the density of trash particles.
Use of large industrial trash compactors is well known. Moreover, it is common to provide a compactor in conjunction with a receptacle so that the two units cooperate to maximize the capacity of the receptacle. Nevertheless, once the receptacle is full, it must still be emptied. Because the receptacle is substantial in size, it must be emptied by a truck that is specially equipped to manipulate the receptacle. The operation and maintenance of such trucks is expensive. Furthermore, the truck operator, referred to as a hauler, is typically paid a certain rate to empty the receptacle based on the number of trips necessary over a period of time. Thus, the more trips made by the hauler, the more expense is incurred by the receptacle user (or owner). To insure that the receptacle does not overflow with trash, many users of these large receptacles require the hauler to empty the receptacles a certain number of days during the week. Consequently, the hauler is paid by the user to empty the receptacle even if it is not full. This accepted method of waste disposal is not cost effective because the hauler is emptying trash receptacles that have unused capacity.
Several prior art methods are known to address the problem of emptying a less-than-full trash receptacle. One such prior art method is to secure a photoelectric cell within the interior of the receptacle. This photoelectric cell senses when the receptacle is full of compacted trash and therefore in need of emptying. This particular method is described in U.S. Pat. No. 3,765,147 to Ippolito.
Use of a photoelectric cell can be inaccurate, however, because it can yield a premature indication that a receptacle is full. For example, if a large volume of highly compactable material such as foam rubber is placed in the receptacle and compacted, the photoelectric cell will nonetheless indicate that the receptacle is full and a hauler would be dispatched to empty the receptacle. However in this instance, more trash could be deposited in the receptacle because the foam gives a false reading having obtained maximum capacity. A similar problem with a photoelectric cell is encountered if a particular trash particle should happen to trigger the cell's sensing mechanism. As a further example, should a long board or the like cover the cell (or a plurality of cells), the photoelectric device will register a full receptacle despite the fact that the board may be the only piece of trash in the receptacle. Of course, it is the nature of trash that it is neither uniform nor predictable in its composition. Thus, the potential for a false reading limits the effectiveness of the photoelectric cell as a measuring or monitoring device.
U.S. Pat. No. 4,773,027 to Neuman teaches another prior art method providing an automated trash management system that monitors the fullness of various receptacles within the system. A plurality of remote status units are set up in operative association with a plurality of containers. The remote status units electronically communicate with a central unit that monitors the fullness of each remote trash receptacle. When the central unit learns that a particular remote compacting unit is full as sensed by the remote status unit, a hauler is notified and dispatched to empty that remote compacting unit. The remote status unit of the Neuman patent employs a sensing device that continuously monitors the maximum pressure of the hydraulic system of the compactor. In other words, rather than utilizing a fixed position sensor as taught by Ippolito, Neuman teaches sensing the maximum amount of pressure for a hydraulic piston used to effect the compacting function in order to determine whether the receptacle is full. In theory, if the receptacle is not full, something less than a predetermined maximum amount of pressure will be detected in the hydraulic system.
However, this prior art method of monitoring the fullness of a receptacle is also limited. First, such a method depends entirely upon pressure within the hydraulic system to determine when the trash receptacle is full. If something other than an hydraulic compaction system is employed, the monitoring function is lost. Of course, should the hydraulic system fail, the monitoring function is likewise lost. Should the system develop a small leak or otherwise be operated inefficiently, the monitoring system may inadvertently give false readings. Further, such an apparatus as taught by Neuman is not tolerant of severe weather conditions experienced in various locations where trash compactors are placed. For example, when the weather is extremely cold, the hydraulic fluid surrounding the piston will become less viscous. The Neuman apparatus may mistake the increase in viscosity of the hydraulic fluid as an increase in the volume of trash compacted within the receptacle provided with the trash compactor, and will consequently wrongly determine that the receptacle is full. Financial resources are wasted in this situation because a hauler will be dispatched to empty a less-than-full container.
Accordingly, there is a need in the art for a cost-effective waste disposal system that monitors the fullness of individual trash receptacles and only dispatches a hauler to empty only a full container. The prior art further needs a waste disposal system that is not limited by mechanical operation of the compactor, but rather enhances such operation as the trash is compacted. As a result, the prior art further lacks a monitoring device what accurately measures the fullness of individual trash receptacles in all types of weather conditions and environments.